This invention relates generally to a process and apparatus for making an air formed article having more than one layer, and especially to a fibrous web and an absorbent core formed by such a web. The absorbent core can be used for applications such as disposable diapers, child's training pants, feminine care articles, incontinence articles, and the like.
In the general practice of forming fibrous articles, it has been common to use a fibrous sheet of cellulosic or other suitable absorbent material which has been fiberized in a conventional fiberizer, or other shredding or comminuting device, to form discrete fibers. In addition, particles of superabsorbent material have been mixed with the fibers. The fibers and superabsorbent particles have then been entrained in an air stream and directed to a foraminous forming surface upon which the fibers and superabsorbent particles have been deposited to form an absorbent fibrous member, such as an absorbent core to be used as part of one of the aforementioned articles. An absorbent core formed in this fashion has a liquid holding formation which is intended to be the primary repository for liquid to be held by the absorbent core. Thus, the liquid holding formation has conventionally been formed to have a greater amount of fibrous and superabsorbent material (SAM) than surrounding regions and is generally thicker than the surrounding regions of fibrous material. In addition, bonding agents or other strengthening components may be incorporated to provide a stabilized absorbent member. The absorbent member may then be stored or immediately directed for further processing and assembly with other components to produce an absorbent article. Other conventional techniques, such as dry-forming techniques, wet-laying techniques, foam-forming techniques, and various wet-forming techniques, have also been employed to form stabilized absorbent members. The resulting absorbent members have included absorbent fibers, natural fibers, synthetic fibers, superabsorbent materials, binders, and strengthening components in desired combinations.
Some absorbent members are formed as a laminate, i.e., a structure having two or more layers. Conventional systems capable of making such articles typically comprise two or more complete independent forming systems, one system for forming each layer after which the layers are combined to make the article. Because the fibers are not substantially commingled at the interface between adjacent layers, the flow of liquid across the interface is inhibited, which is undesirable. The use of such systems also typically requires a large capital expenditure, and space requirements make such systems costly and often undesireable. Further, the implementation of two forming systems requires phase adjustments between the two systems to ensure that the product components by the systems are in proper registration with respect to one another in the final product. If the systems are out of phase, defective products are manufactured and waste is induced, further increasing manufacturing costs.